Field of the Invention
The present invention relates to an image reading apparatus and an image forming system.
Description of Related Art
Heretofore, an image forming system consisting of an electrophotographic image forming apparatus and an image reading apparatus has been used. The image forming apparatus is capable of successively printing images on sheets. The image reading apparatus is capable of reading an image printed on a sheet and performing various types of processes. The image reading apparatus reads an image on a sheet by the use of a scanner which reads the image by irradiating the sheet with light which is emitted from a point light source.
The scanner is provided with a control board which controls an LED element used as a point light source. However, since the control board can be a heat generation source, the light emitted from the LED element may have an unstable luminance. The control board is thereby provided with a heat sink through which heat of the control board is released. Furthermore, as illustrated for example in Japanese Patent Published Application No. 2001-16373, a heat sink is cooled by a fan to effectively dissipate heat from the heat sink and stabilize the luminance of the LED element. The heat generation source can thereby be continuously cooled to inhibit the illumination variation of the LED element and stabilize the luminance.
Incidentally, another image reading apparatus is proposed which can eliminate unevenness of the temperature among a plurality of light sources by providing each light source with a thermoelectric device which cools the light source (for example, refer to Japanese Patent Published Application No. 2011-97348).
However, in the case of the technique described in Japanese Patent Published Application No. 2001-16373, while cooling the point light source, a cooling air can enter a route of conveying a sheet. If a cooling air enters a route of conveying a sheet, there may be caused imbalance of the surface temperature of a sheet in the form of a temperature gradient. In the case where a temperature gradient is formed on a sheet, a scanner may fail to correctly detect a color tone of an image printed on the sheet because of thermochromism which changes a color tone due to a change in temperature.
On the other hand, in the case of the technique described in Japanese Patent Published Application No. 2011-97348, a temperature gradient on a sheet is not taken into consideration so that it is not assumed that cooling heat is transferred to a sheet from each light source.
Accordingly, in the case of the prior art techniques described in Japanese Patent Published Application No. 2001-16373 and Japanese Patent Published Application No. 2011-97348, even if a scanner reads an image, there is the fear that correct color tones can not be detected from an image printed on a sheet due to thermochromism.
The present invention is made in order to solve such a prior art problem and it is an object of the present invention to provide an image reading apparatus and an image forming system capable of detecting correct color tones of an image printed on a sheet.